This application is based on Japanese Patent Application No. 10-306132 (1998) filed Oct. 27, 1998, the content of which is incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a printing apparatus and method using matrix pattern processing and a data processing method. More particularly, the present invention relates to a printing apparatus, a printing, method and a data processing method capable of uniforming the use frequency of each printing element (also referred to as printing component).
It is possible to use various types of printing elements as printing components in accordance with printing systems. For example, in case of an ink-jet printing system, it is possible to use a nozzle for ejecting ink from an ink ejection port as an ink-jet printing element. (Ejecting means for ejecting ink from a nozzle is also referred to as printing element.) Moreover, in case of the ink-jet printing system, it is possible to eject not only a printing ink but also a picture-quality improver for insolubilizing or coagulating color materials in the printing ink.
Moreover, the present invention can be applied to every unit using a printing medium such as paper, cloth, leather, nonwoven fabric, OHP sheet or the like, furthermore metal or the like. As specific applicable units, there are office units such as a printer, a copying machine and a facsimile machine, and industrial production units.
2. Description of the Related Art
As for a printing apparatus, resolution has been improved so far in order to improve image quality. However, a problem occurs that the data processing time by a host computer (host apparatus) or the data transfer time from the host computer to a printer (printing apparatus) increases because data content to be processed increases by improving the resolution.
The conventionally-known matrix printing method solves the above problem. This is a method of transferring image data to which relatively-low resolution processing and high-value quantization processing are applied by a host computer to a printer and developing received image data into print data corresponding to a predetermined dot matrix and printing the data. An example will be described below by referring to FIG. 8. FIG. 8 shows (A) high-resolution processing (600 ppi (pixel per inch)) and (B) matrix pattern processing (300 ppi) as processings by a host computer.
In case of the high-resolution processing (A), by performing quantization processing at 2 levels for 600 ppi, 4-dot printing unit is obtained for 300 ppi and actual printing-dot layouts include 16 types as shown in FIG. 8. Substantial concentration levels of the 16 types of layouts can be handled similarly to the number of dots xe2x80x9c0xe2x80x9d to xe2x80x9c4xe2x80x9d to be applied to a printing area every 4 dots (300 ppi) and the number of concentration levels becomes 5. Moreover, in case of the matrix pattern processing (B), by performing quantization at 5 levels for 300 ppi, each quantized level is assigned to the number of dots xe2x80x9c0xe2x80x9d to xe2x80x9c4xe2x80x9d to be applied to a printing area every 4 dots (300 ppi) as shown in FIG. 8. Thereby, even if data content is decreased, it is possible to perform gradation expression similarly to a printing result by the high-resolution processing.
However, the printing method using the matrix pattern processing (B) in FIG. 8 has the following problem.
That is, because the same matrix pattern (hereafter also referred to as pattern) is used for each concentration level, a difference occurs between use frequencies of a printing component (or an ink-jet printing element serving as a nozzle for ejecting ink in case of the ink-jet printing method). For example, in case of the dot layouts at level 1 and level 3 of (B) in FIG. 8, the use frequency of the nozzle forming upper-side dots becomes larger than that of the nozzle forming lower-side dots. In general, a printing element such as a nozzle is deteriorated in accordance with its use frequency.
To decrease the difference between use frequencies of the above printing element, there is a method of preparing a plurality of patterns for the same concentration level and properly selecting and using them. As an example of the method, a plurality of patterns for level 1 of the matrix pattern processing of (B) in FIG. 8 will be described by referring to FIGS. 9A and 9B. The dot layout at concentration level 1 includes patterns 2, 3, and 4 shown in FIG. 9B in addition to a pattern 1 corresponding to the pattern shown by (B) in FIG. 8 and therefore, includes the total of four patterns as dot patterns for expressing the same concentration level. By properly selecting and using these patterns, it is possible to uniform the use frequency of each nozzle while keeping a concentration level.
However, because the above method selects and uses a plurality of matrix patterns while printing an image, a problem occurs that the noise in a printed image increases or a texture occurs to deteriorate the image.
The present invention is made to solve the above problem and its object is to provide a printing apparatus, a printing method and a data processing method capable of uniforming the use frequency of each printing component while preventing noise or texture from occurring and preventing the printing component from locally deteriorating in a printing system using matrix pattern processing.
In the first aspect of the present invention, there is provided a printing apparatus for printing an image on a printing medium in accordance with print data obtained through a development which develops quantized image data by using a pattern corresponding to the quantized level of the image data, comprising:
setting means capable of selectively setting more than one type of the pattern for at least one quantized level of the image data;
detection means for detecting the discontinuous area of the image to be printed on the printing medium; and
change means for changing types of the patterns to be set by the setting means when the image currently printed on the printing medium reaches the discontinuous area of the image to be detected by the detection means.
In the second aspect of the present invention, there is provided a printing method for printing an image on a printing medium in accordance with print data obtained through a development which develops quantized image data by using a pattern corresponding to the quantized level of the image data, comprising the steps of:
preparing more than one type of the pattern for at least one quantized level of the image data;
changing types of the patterns to be used when the image currently printed on the printing medium reaches a discontinuous area of the image;
developing the quantized image data to the print data in accordance with the pattern; and
printing the image in accordance with the print data.
In the third aspect of the present invention, there is provided a data processing method for processing data to be used in a printing apparatus for printing an image on a printing medium, comprising the steps of:
quantizing an image data corresponding to the image to be printed on the printing medium;
detecting a discontinuous area of the image to be printed on the printing medium in accordance with the image data; and
selecting a pattern corresponding to the quantized image data; wherein more than one type of the pattern corresponding to a predetermined quantized level is prepared, the pattern corresponding to the quantized image data is selected from among the more than one type of the patterns corresponding to the predetermined quantized level, and the selected pattern is changed in accordance with detection results of the detecting step.
The present invention makes it possible to uniform the use frequency of each printing element and prevent the printing element from locally deteriorating by preparing a plurality of matrix patterns for a quantized level of image data while preventing noise or texture from occurring by changing types of matrix patterns to be used when an image currently printed on a printing medium reaches the discontinuous area of the image.